1. Field of the Invention
This invention pertains in general to the treatment of waste anesthetic gases from healthcare or other facilities that use inhaled anesthetics for medical or veterinary purposes. In particular, the invention pertains to a scavenging method and apparatus for collection of waste anesthetic gases produced by an anesthesia delivery system of the healthcare facility, such as a conventional anesthesia machine or a ventilator with sedation capabilities.
2. Description of the Prior Art
Anesthesia delivery systems, such as anesthesia machines in surgical facilities, both hospital and outpatient units, produce significant quantities of waste anesthetic gases. These gases are collected from the patients' exhalation by a central vacuum system. The healthcare facilities typically employ vacuum pumps to collect waste gases from anesthetizing locations. Waste anesthetic gases are pumped to the outside of the medical facility, where the gases are vented to the atmosphere outside the medical facility.
However, healthcare personnel operating the anesthesia machines, may omit to connect the anesthesia machine's exhaust to the central vacuum system. This may happen unintentionally by mistake, or intentionally, for instance during patient transport. In this case the stream of waste anesthetic gases from the anesthesia delivery system escapes to the ambient environment surrounding the anesthesia delivery system. This is undesired as the healthcare personnel is exposed to the waste anesthetic gases and likely breathes in and gets affected or harmed by these gases.
Moreover, vacuum systems have a limited evacuation capacity. When peak flows exit the anesthesia delivery system, as for instance may occur when ventilating the patient with large minute volumes, the gas flow exiting the anesthesia machine partly leaks out to the ambient environment thereof. This leakage has the same disadvantageous effect as cited above, because healthcare personnel is exposed to the leaking waste anesthetic gases.
U.S. Pat. No. 5,044,363 discloses adsorption of anesthetic gases from anesthesia delivery systems by charcoal granules. A cartridge loosely containing powdered activated charcoal is connected to an anesthetic administration system. Waste anesthetic gases are directed through the activated charcoal, achieving removal of approximately 95% of anesthetic substances that otherwise would be released. However, the cartridge described in U.S. Pat. No. 5,044,363 is of relatively large size and devised for facilities that lack a central vacuum system. Furthermore, the cartridge does not provide information about its remaining efficiency and has to be regularly replaced by a fresh cartridge, which is less economical. It is also difficult to determine when a replacement is needed without risking the leakage of anesthetic gas. Moreover, the cartridge has a rather large flow resistance, which is disadvantageous for most anesthesia machines as a pressure is built up upstream the cartridge. This may deteriorate the performance of the anesthesia machine as for instance the regulation of an expiratory pressure is rendered more difficult. Also, the cartridge may leak at high flow rates, as described above.
EP-A2-1142602 discloses an anesthetic gas filter for connection to an anesthesia delivery system and for absorbing or adsorbing anesthetic gas. The anesthetic gas filter has an inlet and an outlet, as well as an adsorbing or absorbing material arranged between the inlet and the outlet of the anesthetic gas filter. The inlet of the anesthetic gas filter is to be connected to an anesthetic machine in order to receive expired gas. The outlet of the anesthetic gas filter is either open or connected to an evacuation line. Thus, the expired gas received from the anesthesia machine into the anesthetic gas filter is always led through the adsorbing or absorbing material of the anesthetic gas filter. Hence, the adsorbing or absorbing material of the anesthetic gas filter is consumed or loaded at every exhalation, constantly deteriorating the efficiency of the anesthetic gas filter in use. The anesthetic gas filter further comprises an anesthetic gas detector arranged in the anesthetic gas filter, such that an early indication of the need to replace the anesthetic gas filter is provided. A replacement of the filter has to be done frequently as the entire anesthetic waste gas is lead through the filter under all operating conditions of the disclosed anesthesia machine. Furthermore, the expiratory resistance added by the anesthetic gas filter to the expiratory branch under all operating conditions, even when connected to an evacuation line, is disadvantageous. The resistance of an expiratory channel is desired to be as low as possible.
Hence, an improved method and apparatus for preventing waste anesthetic gases from escaping to the ambient environment surrounding an anesthesia machine, connectable to a vacuum system, would be advantageous and in particular allowing for increased flexibility and/or cost-effectiveness.